open-consul/agent/connect/ca/common.go

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package ca
import (
"bytes"
"crypto/x509"
"fmt"
"github.com/hashicorp/consul/agent/connect"
)
func validateSetIntermediate(
intermediatePEM, rootPEM string,
currentPrivateKey string, // optional
spiffeID *connect.SpiffeIDSigning,
) error {
// Get the key from the incoming intermediate cert so we can compare it
// to the currently stored key.
intermediate, err := connect.ParseCert(intermediatePEM)
if err != nil {
return fmt.Errorf("error parsing intermediate PEM: %v", err)
}
if currentPrivateKey != "" {
privKey, err := connect.ParseSigner(currentPrivateKey)
if err != nil {
return err
}
// Compare the two keys to make sure they match.
b1, err := x509.MarshalPKIXPublicKey(intermediate.PublicKey)
if err != nil {
return err
}
b2, err := x509.MarshalPKIXPublicKey(privKey.Public())
if err != nil {
return err
}
if !bytes.Equal(b1, b2) {
return fmt.Errorf("intermediate cert is for a different private key")
}
}
// Validate the remaining fields and make sure the intermediate validates against
// the given root cert.
if !intermediate.IsCA {
return fmt.Errorf("intermediate is not a CA certificate")
}
if uriCount := len(intermediate.URIs); uriCount != 1 {
return fmt.Errorf("incoming intermediate cert has unexpected number of URIs: %d", uriCount)
}
if got, want := intermediate.URIs[0].String(), spiffeID.URI().String(); got != want {
return fmt.Errorf("incoming cert URI %q does not match current URI: %q", got, want)
}
pool := x509.NewCertPool()
pool.AppendCertsFromPEM([]byte(rootPEM))
_, err = intermediate.Verify(x509.VerifyOptions{
Roots: pool,
})
if err != nil {
return fmt.Errorf("could not verify intermediate cert against root: %v", err)
}
return nil
}
func validateSignIntermediate(csr *x509.CertificateRequest, spiffeID *connect.SpiffeIDSigning) error {
// We explicitly _don't_ require that the CSR has a valid SPIFFE signing URI
// SAN because AWS PCA doesn't let us set one :(. We need to relax it here
// otherwise it would be impossible to migrate from built-in provider to AWS
// in multiple DCs without downtime. Nothing in Connect actually checks that
// currently so this is OK for now but it's sad we have to break the SPIFFE
// spec for AWS sake. Hopefully they'll add that ability soon.
uriCount := len(csr.URIs)
if uriCount > 0 {
if uriCount != 1 {
return fmt.Errorf("incoming CSR has unexpected number of URIs: %d", uriCount)
}
certURI, err := connect.ParseCertURI(csr.URIs[0])
if err != nil {
return err
}
// Verify that the trust domain is valid.
if !spiffeID.CanSign(certURI) {
return fmt.Errorf("incoming CSR domain %q is not valid for our domain %q",
certURI.URI().String(), spiffeID.URI().String())
}
}
return nil
}